import scipy.stats as st
import matplotlib.pyplot as plt
from numpy import linspace 
from math import sqrt,exp,log

n=50
norm=st.norm.pdf
chi2=st.chi2.pdf
xx=linspace(n-20,n+20)
plt.plot(xx,norm(xx,n,sqrt(2*n)),c='green',label='normal')
plt.plot(xx,chi2(xx,n),c='red',label='chi2')

plt.legend()

plt.show()